Rice Husk Research Articles

Enhancement of nutrient use efficiency with biochar and wood vinegar: A promising strategy for improving soil productivity.

The co-application of biochar and wood vinegar has demonstrated the potential to enhance premium crop production. The present study reveals the effects of co-applying rice husk biochar and wood vinegar (both foliar and soil application) on soil properties and the growth of Chinese cabbage (Brassica chinensis L.) in a two-season pot experiment. The soil pH, electrical conductivity and dissolved organic carbon contents in combination treatments of wood vinegar and biochar were increased more when wood vinegar was applied to soils rather than to leaves, and the parameters were observed to surpass those for chemical fertilizer treatments. The biomass of Chinese cabbage shoots was significantly increased by 60.8- and 27.3-fold in the combined treatments compared to the control when 1% wood vinegar was sprayed to the leaves (WF1) in 2022 and 2023, respectively. Higher contents of vitamin C, soluble protein and soluble sugar were also observed in the combined wood vinegar and biochar treatments compared to chemical fertilizer treatments and the control; for example, the vitamin C content of plant shoot in WF1 was 21.3 times that of the control. The yield and quality of plants were decreased across all treatments in 2023 compared to 2022 but the combination treatments still displayed superiority. The co-application of wood vinegar and biochar enhances the growth and improve the quality of Chinese cabbage through improving the soil properties and plant photosynthesis. Moreover, the foliage application of wood vinegar is more preferable compared to soil application. © 2024 Society of Chemical Industry.

Soil remediation and nano-biosilica: a potential combination to improve the environmental quality of brackishwater aquaculture ponds affected by acid sulfate soils.

The successful management of ASS-affected brackishwater aquaculture ponds necessitates overcoming associated environmental limitations. This study investigated the potential application of nano-biosilica from rice husk ash (RHA) and soil remediation techniques to improve the environmental quality of ASS-affected brackishwater ponds. The study followed a completely randomized design (CRD) with four treatments and three replicates. The treatments comprised applying soil remediation, nano-biosilica fertilizer, and their combination. The study generally revealed that the combination of soil remediation technique and RHA-driven nano-biosilica improved the water quality of ASS-affected brackishwater ponds. Soil remediation improved water quality by reducing acidity levels. However, excessive lime application as an integral part of the remediation might release acidity and toxic metals into water, potentially increasing calcium-phosphorus fixation. Despite liming potential negative consequences, if mixed with nano-biosilica could increase diatom-phytoplankton growth by reducing dissolved Al and Fe levels while boosting P and Si availability. Liming could also help boost diatom photosynthesis and inhibit unwanted algae blooms by decreasing water turbidity and increasing sunlight penetration. This study emphasized that the effectiveness of nano-biosilica in promoting diatom growth depends on appropriate nitrogen (N) and phosphorus (P) concentrations and ratios, which should not be a limiting factor. However, the required N/P concentration and ratio are only met if the remediation method is effectively implemented. The combination of nano-biosilica and soil remediation treatment maintained SiO2 concentrations above the average natural seawater concentration; however, availability may be limited due to complexes containing Ca, Al, Mg, and Fe. Regularly applying cost-effective nano-biosilica fertilizer in combination with N and P fertilizers is recommended to enhance water remediation efficiency by boosting Si availability and decreasing the toxicity of dissolved toxic metal ions.

Preparation of Sustainable Ni/SiO2 Catalysts from Rice Husk by Different Methods for CO2 Methanation.

Silicon dioxide (SiO2) from rice husk can be extracted and be used as support for Ni-based catalysts. The impregnation method (IM) is usually used for preparing Ni/SiO2 catalysts, but its catalytic activity in CO2 hydrogenation to CH4 remains unsatisfactory. In this work, we explored alternative preparation methods, using ammonia evaporation method (AEM) and hydrothermal method (HM) to prepare the catalysts. The results showed that the catalysts prepared by AEM and HM were significantly superior to that prepared by IM. Notably, the catalyst synthesized by AEM from sustainable silica exhibited the best performance, achieving 81.69% CO2 conversion and over 99% methane selectivity at low reaction temperature of 300 °C. The characterization techniques indicate that the Ni/SiO2-AEM catalyst can form nickel phyllosilicate with lamellar structure, leading to better Ni dispersion and higher specific surface area. Furthermore, the results of in-situ DRIFTS have revealed the potential catalytic mechanism over Ni/SiO2 catalysts, indicating that it involves pathways with both the CO* and HCOO* as the key intermediates.

Exploring the influence of different precursor materials on the catalytic performance and deactivation characteristics of iron-loaded biochar catalysts for the catalytic cracking of toluene

This study employed rice husks (RH), corn stalks (CS), and camphor leaves (CL) as biomass sources to prepare iron-loaded biochar catalysts, elucidating the key relationships between these biomass materials, their catalytic performance, and their resistance to deactivation in toluene. Experimental results indicated that the carbon deposits in the three spent catalysts are primarily composed of inert carbon (Cγ). The carbon peaks in these deposits primarily consisted of CO, CC, and CO structures, with varying proportions across the different types of spent catalysts. Specifically, the RH spent catalyst exhibited the highest relative content of the CO structure at 13.49 %, the CS spent catalyst showed the highest relative content of the CC structure at 89.19 %, and the CL spent catalyst displayed the highest relative content of the CO structure at 5.57 %. Fe2+ was the predominant species on the surfaces of all three spent catalysts, accounting for over 50 % in each case. Fe3C was detected on the surfaces of the CS and CL spent catalysts but was absent on the RH spent catalyst. After 80 min of reaction, the carbon deposition rate of the CL catalyst was 8.15 %, with a catalytic cracking efficiency of 28.04 %, making it the most effective overall. This effectiveness was attributed to the CL catalyst's highest oxygen vacancy intensity, where the abundant oxygen source effectively promoted the catalytic reaction of toluene and inhibited carbon deposition. After three consecutive regeneration cycles, the catalytic cracking efficiency of the CL catalyst remained above 70 %, demonstrating strong cyclic regeneration performance. This study provides theoretical insights into the effective utilization of agricultural and forestry waste, contributing to environmental protection.

Selection of sustainable construction material from recycled waste plastics by q-rung orthopair fuzzy SWARA-MABAC approach

Recycling of waste plastics and agro-industrial waste for the development of sustainable polymeric composites is recognized as a viable approach to overcome the detrimental environmental effects of plastics waste. Despite of immense potential of sustainable composites in the Circular Economy (CE), its implementation is still insignificant due to the lack of an effective material selection approach. The existence of several influencing aspects in the process of material selection considers it a multi-criteria decision making (MCDM) problem. In the present work, an Aggregation Operator (AO) based integrated Stepwise Weight Assessment Ratio Analysis (SWARA) and Multi-attributive Border Approximation Area Comparison (MABAC) has been proposed to deal with the issues of material selection for polymer based sustainable composites. Moreover, q-rung orthopair fuzzy numbers (q-ROPFNs) have been implemented to tackle the uncertainty in the information. The effectiveness of the proposed approach has been confirmed by different comparative and sensitivity investigations. The developed composites have shown excellent properties whereas the responses of the materials vary invariably with compositions. The proposed method has identified the amalgamation of 10 wt percentage of rice husk ash and 10 wt percentage of sand with 80 wt percentage of high-density polyethylene (HDPE) as an appropriate material for the development of sustainable floor tiles as the composites resulted to optimum mechanical performances and minimum abrasive wear. The proposed model gives reliable and robust results and is sensitive to the criteria weights and mathematical parameters. The outcome of the research has exposed that the suggested mathematical approach can be effectively applied for material selection of sustainable polymeric composites for different applications.

Performance assessment of pervious concrete incorporated with calcium silicate hydrates (C-S-H) cultivated on rice husk ash substrates – A trend surface analysis interpretation

Pervious concrete is a special type of concrete designed to allow water to pass through by omitting fine aggregates from the mix, or by using special techniques to create interconnected voids within the concrete. The current study investigates a novel method of cultivating calcium silicate hydrate (CSH) precipitates on a supplementary cementitious material (SCM), Rice husk ash (RHA), substrate and integrating the RHA substrate into pervious concrete to improve mechanical and durability properties. Scanning electron microscopy (SEM) images indicates the formation of precipitates of calcium silicate hydrates on the surface of RHA particles. The silica to RHA (Si/RHA) ratio and curing age of pervious concrete specimens serve as focal points for assessing the mechanical characteristics. Trend surface analysis is utilized to analyse the results, using a polynomial equation to identify underlying trends or patterns within the dataset. The analysis reveals that the Si/RHA ratio and curing days have minimal impact on permeability, while an increase in RHA substrate volume reduces permeability, indicating microstructure densification rather than macro void filling. For compressive strength, the results show that higher Si/RHA ratios and longer curing times positively correlate with strength, with accelerated hydration suggested by the quadratic coefficients of curing age. In terms of split tensile strength, increasing substrate volume enhances strength, while linear terms of Si/RHA ratio and curing age also exhibit positive correlations, although quadratic terms indicate minimal change in strength gain rates. Flexural strength correlates positively with both Si/RHA ratio and curing age, while abrasion resistance negatively correlates with Si/RHA ratio and substrate volume, suggesting enhanced resistance with increased values. CSH seeds grown on RHA enhances the microstructure of concrete, resulting in a denser material facilitating rapid strength development and improved durability.

Enhanced‐Performance Electrodes from Biomass‐Derived Carbon (Rice Husk) for Printable Perovskite Solar Cells

In the quest for sustainable energy solutions, printable carbon‐based perovskite solar cells (p‐MPSCs) are capturing the industry's attention due to their exceptional stability, simplified assembly, and cost‐effectiveness. At the heart of this innovation lies the carbon electrode, favored for its straightforward printing and assembly processes, making it an ideal candidate for renewable photovoltaic applications that leverage biomass carbon. This study casts the spotlight on rice husks, a plentiful yet underutilized resource, repurposing them into carbon electrodes for p‐MPSCs through a specialized carbonization treatment. A comprehensive examination reveals that the integration of 20% rice husk carbon (RHC) with graphite significantly improves the material's filling and crystalline qualities, diminishes the density of defect states, and strengthens the suppression of nonradiative recombination. These advancements culminate in a notable increase in photovoltaic conversion efficiency, reaching up to 11.49%. This study not only demonstrates the viability of RHC in photovoltaic applications but also supports the efficient use of biomass carbon, contributing to the progression of green energy technologies.

Predicting mechanical properties of sustainable green concrete using novel machine learning: Stacking and gene expression programming

Abstract Using rice husk ash (RHA) as a cement substitute in concrete production has potential benefits, including cement consumption and mitigating environmental effects. The feasibility of RHA on concrete strength was investigated in this research by predicting the split tensile strength (SPT) and flexural strength (FS) of RHA concrete (RHAC). The study used machine learning (ML) methods such as ensemble stacking and gene expression programming (GEP). The stacking model was improved using base learner configurations ML models, such as, random forest (RF), support vector regression, and gradient boosting regression. The proposed models were validated by statistical tests and external validation criteria. Moreover, the effect of input parameters was investigated using Shapley adaptive exPlanations (SHAP) for RF and parametric analysis for GEP-based models. The analysis revealed that the stacking ensemble integrates base learner predictions and demonstrated superior performance, with R values greater than 0.98 and 0.96. Mean absolute error and root mean square error values for both SPT and FS were 0.23, 0.3, 0.5, and 0.7 MPA, respectively. The SHAP analysis demonstrated water, cement, superplasticizer, and age as influential parameters for the RHAC strength. Furthermore, the SPT and FS of RHAC can be predicted with an acceptable error using the GEP expressions in the standard design procedure.

Environmental assessment of alkali-activated materials based on agro-industrial waste as alkaline activators through leaching tests

Global circular economy drives the development of sustainable alkali activated materials (AAM) for use as construction material from industrial by-products and wastes. The assessment of the potentially hazardous substances release of these new material combinations into the soil and groundwater over time is essential. In this study, the aim is the environmental assessment of three AAMs based on blast furnace slag (BFS), activated with almond shell biomass ash (ABA) as potassium source and three solid sources of silica from the agricultural industry, rice husk ash (RHA), spent diatomaceous earth (SDE) and bamboo leaf ash (BLA), using European horizontal leaching tests proposed for construction materials, for monolithic form, Dynamic Surface Leaching Test (DSLT) and for granular form, Up-flow Percolation Test and the Compliance leaching test, by simulating different scenarios of their entire life cycle. The leaching results of the AAM showed the effectiveness of the inertization of all the recycled materials studied, which exceeded some inert materials limits, by means of the activation process. Despite the absence of significant differences in the leaching mechanisms of the oxyanions As, Cr, Mo, Sb, Se and V between the three AAMs developed, they presented different long-term leaching behavior depending on their form, monolithic, or granular, and therefore in their different life cycle stages. Therefore, it is concluded that although the incorporation of agro-industrial waste as alternative activators in BFS based AAM according to the Dutch Soil Quality Decree (for unrestricted use of monolithic and granular materials) is an environmentally acceptable option, the design of waste derived AAMs should be assessed by means of a combination of leaching tests that cover their expected life cycle.

Short-Term Effect of the Combined Application of Rice Husk Biochar and Organic and Inorganic Fertilizers on Radish Growth and Nitrogen Use Efficiency.

Research on soil biochar fertilization has mainly been conducted on cereal crops, and information on its potential for radish production remains inconsistent. Therefore, a pot experiment was conducted to examine the short-term effects of rice husk biochar on radish growth and nitrogen use efficiency (NUE). An investigation was conducted with two application rates of biochar alone, (10 t ha-1 (B10) and 25 t ha-1 (B25), and biochar + chicken manure application with and without NPK fertilizer. The results indicated that the application of biochar 25 t ha-1 + chicken manure (B25:CHM) and the combination of biochar 25 t ha-1 + chicken manure + NPK fertilizer (B25:CHM:NPK) significantly increased root yield by improving NUE, fertilizer recovery efficiency (REN), agronomic efficiency (AE), nitrogen harvest index (NHI), and retaining soil NH4+-N. Although biochar application alone did not significantly influence radish growth on a short-term basis, B10 and B25 increased root yields by 10% and 20%, respectively, compared with the control. Notably, the role of biochar application when combined with organic and inorganic fertilizers was to retain fertilizer N and promote N uptake efficiency by radishes, as higher rates of biochar resulted in higher NUE. Our results suggest that B25:CHM is a suitable combination for organic farming.

Self-ignition behaviour of corn cob, wheat bran and rice husk residues in ambient air from biomass gasification

The possibility of different agrowastes to self-ignite under ambient condition, due to exothermic reactions between their surface molecules and air or other oxidizing agents which are conveyed into the void volume between the particles, exists. It is imperative to investigate the self-ignition ability of these harzadous waste products causing environmental pollution after the milling process to avoid sudden fire outbreaks. In this study, the self-ignition attributes of corn cob, wheat bran and rice husk residues in ambient air from biomass gasification was investigated by evaluating their self-ignition temperatures using DIN EN 15188:2021 standard and Frank-Kamenetzkii's theory of thermal explosion at varying basket volume. The results revealed decrease in the ignition temperature of dust samples as ignition time and dust basket volume were increased. Sample C (rice husk dust residue) was considered to be the most hazardous with respect to its propensity to self-heating possessing the lowest self-ignition temperature of 173 °C at 800 mL cubic mesh. Its moisture content and activation energy of 1.41 % and 46.52 kJ/mol respectively were the lowest. Its thermal conductivity, carbon content, heating value and bulk density of 0.07 W/mK, 78.98 wt%, 26,895 kJ/kg and 255.4 kg/m3 respectively were the highest. Correlation coefficient from the Arrhenius plot showing the self-ignition behaviour of dust samples using the model of Frank-Kamenetzkii were 0.9976, 0.9910 and 0.9962 for corn cob, wheat bran and rice husk residues respectively. In conclusion, the data presented are effective in predicting the self-ignition ability of corn cob, wheat bran and rice husk residues in ambient air from biomass gasification in order to prevent sudden fire attack that may arise based on storage of their dust particles in food processing industries.

Thermodynamic analysis on the coupling effects of operating parameters in sorption-enhanced chemical looping gasification with rice husk as feedstock

Sorption-enhanced chemical looping gasification (SECLG) has a favorable ability to produce H2-rich syngas without any extra separation process. To comprehensively investigate the performances, the temperature in the fuel reactor (FR) side TFR, molar ratio of steam or CaO to carbon (λsteam/C, λCaO/C), circulation ratio of oxygen carrier to carbon (λOC/C) are changed to test their effects on the products. Then the coupling effects on SECLG are deeply analyzed by changing two and three of the operating parameters. Results demonstrate that under fundamental conditions, the sorption enhancement becomes unavailable when the temperature is higher than 775 °C but decreasing λsteam/C and increasing λOC/C can elevate this critical temperature. Increasing the λOC/C or λsteam/C can enhance the H2 concentration first, then weaken H2 concentration. The maximum value of H2 concentration is 62.47% when λOC/C = 0.4 and λsteam/C = 1.9. When the FR temperature is lower than 775 °C, there is an optimal λOC/C for maximizing the H2 concentration at a specific temperature. When the temperature is 650 °C, λOC/C = 0.5 and λsteam/C = 1.9, the maximum value of H2 concentration can reach 95.73% in SECLG.

Study on using waste biomass as carbon reducing agent in industrial silicon smelting

In this study, seven types of biomass (coffee husk, macadamia husk, peanut husk, rice husk, rice straw, tobacco straw, and cotton straw) were carbonized at temperatures ranging from 300 °C to 1000 °C. This study explored the potential of these biomass samples as carbon reducing agents for industrial silicon and compared them with charcoal in terms of their proximate analysis, electrical resistivity, and apparent activation energy of the reaction. The results indicated that as the pyrolysis temperature increased, the oxygen content and aliphatic functional groups in biochar gradually decreased, as did the volatiles content, while the proportions of fixed carbon and ash increased. The resistivity decreased upon the removal of volatiles and an increase in the degree of graphitization. At 600 °C, the fixed carbon content of all biochar exceeded 65%, and the fixed carbon content of macadamia husk biochar reached 91.32%, which was higher than that of charcoal (81.44%), the maximum specific surface area was 335.706 m2/g, which was much higher than that of charcoal (5.705 m2/g). Thermogravimetric analysis and kinetic analysis indicated that coffee husk had better reactivity than charcoal. The gasification reactivity of coffee husk was R = 3.1949%/min °C, which was higher than that of charcoal (0.7930 %/min °C). The apparent activation energy during the coking reaction stage was 51.86 kJ/mol, which was lower than that of charcoal (98.9 kJ/mol). Overall, biochar had a suitable fixed carbon and electrical resistivity at 600 °C and can be used as a carbon reducing agent for industrial silicon, among them, macadamia husk with high fixed carbon and coffee husk with high reactivity have greater application potential.

An Assessment of the Impact of Locally Recycled Cementitious Replacement Materials on the Strength of the Ultra-High-Performance Concrete

Withstanding extreme events is increasingly a significant challenge for the construction industry. Where civil infrastructures remain using traditional concrete, which has low tensile strength, poor durability, and weak crack resistance, in this regard, ultra-high-performance concrete (UHPC), with its outstanding mechanical properties and high strength, offers the prospect of wide application. This advanced technology allows for the fabrication of thin and light-dimensional structures to accelerate construction while increasing corrosion resistance to minimize maintenance intervention and extend the service life of the infrastructures. Despite this, UHPC is less eco-friendly due to consuming more cement than the usual material, which requires replacement materials, such as silica fume (SF) and rice husk ash (RHA), which are readily available from other local material production. This study proposes an experimental approach to assess the influence of SF and RHA content on the properties of UHPC. Different SF and RHA compositions will be adjusted to analyze their effects on slump flow, compressive strength, flexural strength, tensile strength, and the stress–strain relationship in UHPC tension testing. Based on the results, the most effective ratio is RHA replacing 50% of the SF in the UHPC mixture. Specialized tensile experiments reveal enhanced tensile strength with judicious RHA incorporation at 5-day and 28-day stages, particularly in initial crack and damage conditions. Stress–strain curves for 5% to 15% RHA samples show increased ductility, indicating that optimal RHA-SF ratios enhance UHPC cracking characteristics. Based on the results, a discussion on the appropriate proportions for utilizing most local materials will be derived, especially for regions of Vietnam. It is evaluated as a feasible and promising solution to reduce greenhouse gas emissions threatening global climate change.

Effect of large particle mixing on cloud ignition and explosion of fine rice husk

Large particles mixed with fine dust are commonly found in the processing and transportation of grain dust. The mixture of dust is exposed to the risk of dust explosions when suspended in the environment. Using a 20 L spherical explosion device and the dust cloud minimum ignition energy (MIE) experimental platform, this study examines the effects of crushed brown rice mixture on the ignition and explosion of fine rice husk dust. The discovery of large granules of crushed brown rice being lifted up to form flow "obstacles" in the mixed dust cloud has a similar inhibitory effect to inert materials, causing the MIE of the dust cloud to increase from 40 mJ to 150 mJ. However, 5 % of crushed brown rice will lower the 10 mJ dust cloud's ignition energy when the concentration of dust clouds is 500 g/m3. Through testing the dispersibility of mixed dust clouds, it was found that fine dust particles adsorbed on the surface of large particles will peel off after being lifted, improving the dispersibility of the mixed dust cloud and forming a system of mixed dust clouds with finer effective particle size, thereby promoting ignition. Furthermore, due to the improvement in the dispersibility of mixed dust clouds by large particles, at mixing ratios below 30 %, large particles will also significantly increase the maximum rate of pressure rise (dP/dt)max, increasing the likelihood of dust ignition and the consequences of an explosion. Therefore, these findings should be taken into consideration during the process of grain processing and transportation.

Investigation of Novel Transition Metal Loaded Hydrochar Catalyst Synthesized from Waste Biomass (Rice Husk) and Its Application in Biodiesel Production Using Waste Cooking Oil (WCO)

The decarbonization of transportation plays a crucial role in mitigating climate change, and biodiesel has emerged as a promising solution due to its renewable and eco-friendly nature. However, in order to maintain the momentum of the “green trend” and ensure energy security, an ecologically friendly pathway is important to produce efficient biodiesel. In this work, activated carbon (AC) obtained from rice husk (RH) is hydrothermally prepared and modified through cobalt transition metal for catalyst support for the transesterification process. The physicochemical characteristics of the synthesized catalysts are examined using XRD, FTIR, SEM and EDS, TGA, and BET, while the produced biodiesel is also characterized using Gas Chromatography and Mass Spectroscopy (GC-MS). To optimize the transesterification process, Fatty Acid Methyl Esters (FAME) are produced by the conversion of waste cooking oil. Response Surface Methodology (RSM) is used to validate temperature (75 °C), the methanol-to-oil molar ratio (1:9), catalyst weight percentage (2 wt.%), and retention time (52.5 min). The highest conversion rate of waste cooking oil (WCO) to biodiesel was recorded at 96.3% and tested as per American Society for Testing and Materials (ASTM) standards. Based on the results, it is clear that cobalt-loaded rice husk-based green catalyst (RHAC-Co) enhanced catalytic activity and yield for biodiesel production. Further research should focus on engine performance evaluation and scaling up of the catalyst by optimizing it for the industrial scale.

Advancing the Sustainability of Geopolymer Technology through the Development of Rice Husk Ash Based Solid Activators

Rice husk ash (RHA), an agricultural waste byproduct, has already been tested as a component in geopolymeric binders, typically as part of the precursor solid mix, alongside materials like fly ash (FA), slag, and cement. This study presents a novel approach where RHA is employed to create a solid activator, aimed at entirely replacing commercial sodium silicates. The synthesis process involves mixing RHA, NaOH (NH), and water by applying a SiO2/Na2O molar ratio equal to 1, followed by mild thermal treatment at 150 °C for 1 h, resulting in the production of a solid powder characterized by high Na2SiO3 content (60–76%). Additionally, microwave treatment (SiO2/Na2O = 1, 460 W for 5 min) increases the environmental and economical sustainability of alkali silicates production from RHA since this processing is 12 times faster than conventional thermal treatment reducing at the same time the final product’s embodied energy. The efficacy of this new material as a sole solid activator for the geopolymerization of Greek FA is investigated through various techniques (XRD, FTIR, SEM). One-part geopolymers prepared with RHA-based solid activators demonstrated mechanical performance comparable to those prepared with commercial products (~62 MPa at 7 days). This research contributes to the advancement of sustainable construction practices emphasizing the importance of local materials and reduced environmental impact in achieving long-term sustainability goals.

Synergistic Freeze-Resistant Strategy of Multi-Stage PCM Concrete Incorporated with Rice Husk Ash and Fly Ash

Synergistic Freeze-Resistant Strategy of Multi-Stage PCM Concrete Incorporated with Rice Husk Ash and Fly Ash

Catalytic pyrolysis of polystyrene over rice husk silica-derived traditional and hierarchical green MWW zeolites

This work aimed at the green synthesis of MWW zeolites using rice husk silica as an alternative raw material. It was also performed a post-synthesis desilication procedure with NaOH and CTABr aiming to obtain MWW zeolites with improved accessibility. The set of characterization techniques (XRD, 27Al MAS NMR, N2 physisorption, SEM, TEM, and Pyridine-FTIR) revealed the phase purity and combined structure of micro-mesopores after desilication. The zeolites were evaluated as catalysts for polystyrene pyrolysis, producing benzene, toluene and ethylbenzene, besides styrene monomers, and dimers. Without any catalyst, polystyrene produces only styrene monomers, dimers and trimers. The desilication increases the amount of Brønsted and Lewis sites and the external area, catalyzing the production of polyaromatics and naphthalene derivatives. The activation energy decreased for the catalyzed reactions, reflecting other reaction pathways.

A review of the use of rice husk silica as a sustainable alternative to traditional silica sources in various applications

A review of the use of rice husk silica as a sustainable alternative to traditional silica sources in various applications